Abstract
In this article, we present the design and analysis of a 785-nW multimodal sensor interface IC for ozone pollu- tant sensing and correlated cardiovascular disease monitoring based on electrocardiography (ECG) and photoplethysmography (PPG). The proposed hybrid dc offset current cancellation (DCOC) along with a 4-M gain-regulated cascode transim- pedance amplifier (RGC-TIA) enable PPG readout power reduc- tion by 37 ×, compared with the state-of-the-art PPG sensor interfaces. The ozone sensing channel proposes an adaptive architecture to enable low V DD operation, achieving a 300 × power reduction, compared with t he state-of-the-art gas sensing readouts. The ozone sensing channel’s performance was also veri- fied using custom resistive metal-oxide sensors for concentrations from 50 to 900 ppb. The sensor interface IC is fabricated in a 65-nm CMOS, integrating a 165-nW voltage-mode ECG channel, a 532-nW current-mode PPG channel, 76-nW resistive-mode ozone channel, and 12.6-nW peripheral circuits, all at 0.6 V . The total system power consumption including the LED and a custom digital readout IC is 10.98–15.51 μW, which is 41×–57× less than prior ozone/CVD joint monitoring sensor interface systems.